1. Field of the Invention
The present invention relates to a method and apparatus for managing a routing area in a mobile communication system, and in particular, to a method and apparatus for managing a routing area in a third generation (3G) mobile communication system and a 3G Long Term Evolution (LTE) communication system.
2. Description of the Related Art
In general, a wireless communication system refers to a system developed in preparation for a case where it is impossible to connect a fixed wire network up to a mobile station. Such wireless communication systems include a wireless Local Area Network (LAN), a Wireless broadband (Wibro) system, a Mobile Ad Hoc network, etc. as well as typical mobile communication systems for providing voice and data services. The mobile communication is intended to enable a subscriber to perform the communication while the subscriber moves at a high speed in a wide area. One representative mobile communication system is a cellular system. In the cellular system, which overcomes both the limit in the service area and subscriber accommodating capability of conventional mobile communication systems, a service area is divided into a plurality of small sections, that is, cells, and two cells located sufficiently far from each other use the same frequency band, thereby spatially reusing of the frequency band. From among such cellular systems, analog type systems, such as Advanced Mobile Phone System (AMPS) and Total Access Communication Services (TACS), have appeared for the first time, and are generally called 1st generation mobile communication systems.
Unfortunately, with 1st generation mobile communication systems, it has become difficult to support the rapidly increasing number of mobile communication service subscribers. Furthermore, along with recent technological developments, requirements for various services have increased beyond the initial voice service. As a result, 2nd generation mobile communication systems having a digital scheme and being more advanced than 1st generation mobile communication systems, have appeared. In a 2nd generation mobile communication system, a voice signal (analog signal) is digitalized (voice encoding) and is then subjected to digital modulation/demodulation, and uses a transmission frequency band of 800 MHz. Furthermore, multiple access schemes were developed and used in 2nd generation mobile communication systems, such as Time Division Multiple Access (TDMA) or Code Division Multiple Access (CDMA) scheme. Here, the 2nd generation mobile communication system provides a voice service and a low speed data service, and includes systems of IS-95 (CDMA scheme) and IS-54 (TDMA scheme) of USA and systems of Global System for Mobile (GSM) communication scheme.
Further, the Personal Communication Services (PCS) system is classified as a 2.5th generation mobile communication system and uses a frequency of 1.8˜2 GHz band. The 2nd generation mobile communication systems have been constructed in order to increase the efficiency of the mobile communication system while providing a voice service to users thereof. However, the appearance of the Internet and users' demand for a high speed data service have predicted the appearance of a new wireless platform, which is the 3rd generation mobile communication, such as International Mobile Telecommunication (IMT) 2000. Despite such development in the communication technology, it is possible to easily predict saturation of currently used wireless electric wave spectrum in view of the current trend of rapid increase in the wireless communication services. Therefore, there has been a request for development of new wireless communication technology having a superior characteristic in the frequency efficiency. A representative example of such wireless communication technology is a spread spectrum scheme.
In communication according to the spread spectrum scheme, a signal is spread and transmitted with a frequency bandwidth much wider than the frequency bandwidth of the signal itself, and it is difficult to detect the existence of the signal because the signal has a low power density. Furthermore, in order to restore the original by de-spreading the received signal, the receiver must know the exact codes used in the spreading. Therefore, the communication security is ensured, and other external disturbing signals cannot disturb the communication because they are spread during the de-spreading.
In such a 3rd generation (3G) mobile communication system, there are, in large part, two methods of constructing a routing area.
The first method is to construct a routing area having a fixed size and a fixed ID by an operator, as used in the current 3G mobile communication system.
The second method is to construct a routing area by flexibly determining the routing area during the routing area update or during attachment of a mobile station by using a radius determining the size of the routing area and a physical location of the cell in which the mobile station is located.
The first method is being used in the current 3G mobile communication system and constructs a routing area having a fixed size defined in advance. However, the first method cannot take the mobility and positional characteristic of a mobile station into account. If a mobile station is located within a vehicle driving in a highway, the mobile station must perform frequent routing area update as the mobile station continuously passes through a plurality of routing areas. In cases where the mobile station has the mobile characteristic as described above, it is possible to reduce the unnecessary signaling overhead for the routing area update by setting the shape of the routing area in consideration of the mobile characteristic of the mobile station.
According to the second method, different routing areas are defined for mobile stations, based on a physical distance value such as a radius from a cell, and a physical location value of the cell in which the mobile station is located. The second method can more flexibly determine the routing area than the first method.
However, a network entity for controlling the mobility of a mobile station, for example, a Serving GPRS Supporting Node (SGSN), must control a routing area constructed by a list of different cells having different sizes for mobile stations. In order to transmit a paging request to a mobile station, the network entity for controlling the mobility of a mobile station must maintain a list for each mobile station, which includes all cells located within a distance of radius R from the mobile station, and then insert the list of all cells included in a corresponding routing area into a paging request message. Otherwise, a Radio Access Network (RAN), such as a Radio Network Controller (RNC), keeps a list for each mobile station, which includes cells belonging to the routing area of the mobile station from among cells controlled by the RNC itself, and broadcasts a paging request message to the corresponding cells.
This method, in which a RAN or a network controls a cell list based on a radius of each mobile station and transmits it through a signaling message as described above, may degrade the capability of the network and the RAN.